For any jammer, the radiation will not exceed the standard only after the distance from it exceeds the "minimum safe distance". The minimum safety distance is related to the safety threshold of the transmit power, antenna gain and radiation field strength, as shown in equation (1):
P・G＜Ｃ・41r・D2
Among them, Prepresents the signal jammer transmit power; G represents the jammer antenna gain; C represents the safety threshold of the radiated field strength, and the value is 10 w/era2; D represents the minimum safety distance of the jammer.
Figure 1 shows the relationship between the minimum safe distance and the total transmit power. When the antenna gain is 3dB, if the minimum safety distance is required to be 2m, the total transmit power should not exceed 2. 5W. Similarly, for any jammer, its effective interference range is limited. This article uses "effective interference radius" to describe the effective interference range of the jammer. The effective interference radius is related to the transmit power of the jammer, the type of communication system being interfered with, the signal strength, the channel model, and the interference mode.
Figure 2 reflects the relative relationship between the effective interference radius and the minimum safety distance under different conditions. The ideal situation is that the minimum safety distance D is small and the effective interference radius R is large to ensure that people in the effective interference zone are not exposed to excessive radiation; but the reality is that D and R are similar, that is, the people in the effective interference zone Exposure to excessive radiation; In extreme cases, D≥R, that is, all people in the effective interference zone will receive excessive radiation.
For the current mainstream swept-frequency indoor jammers, when interfering with medium-strength communication signals, the effective interference radius is about 6m, the total transmission power is about 15W, the antenna gain is 2-3dB, and the safe distance is about 5m. It can be seen that in this scenario, the health of most participants will be affected by the jammer radiation.
There are many reasons for this problem. In addition to the above-mentioned anti-interference technology use, wide bandwidth, multiple frequency bands, and frequency sweeping interference methods, there are also provisions for combating small-scale fading and occlusion during wireless signal propagation. The power headroom. For jammers, the anti-interference technology, bandwidth and frequency band, and wireless signal propagation characteristics of the communication system cannot be changed. What can be changed is the interference method and the interference object. The most important thing is how to bypass the anti-interference of the communication system. design.
